Abraham Lincoln is shown in his youth addressing an audience of village people on the street corner. A terrific thunder storm comes up, driving his auditors away, and Lincoln mounts his horse and rides away. The storm increases in fury, and Lincoln is compelled to seek shelter at a farm house, owned by a widow, Mrs. Barnes, who has a son about ten years of age, named Harry. Mrs. Barnes prepares a hearty meal for Lincoln, who dries himself at the hearth, and when the storm has ceased wishes to pay Mrs. Barnes for the meal. Knowing his poverty, she refuses to accept anything, and Lincoln gravely gives her an I.O.U., reading: "I.O.U. the price of one good meal. Also my life, as I might have lost it in the storm. Abe Lincoln, Lawyer." Ten years later the Civil War breaks out, and Harry Barnes enlists. During the course of the war the Union soldiers take up headquarters with a Southern family, and Harry meets Betty and falls in love with her, and secures her promise to marry him after the war is over. As the Union soldiers move on they are caught in an ambush, and Harry's horse is shot from under him. He leans into the thicket and in a running fight with his pursuers manages to elude them and takes refuge at Betty's home. Betty is fearful that Harry will be captured, and provides him with a suit of civilian's clothes, and that night he endeavors to steal back to his regiment. He is captured, however, and according to military rules is held as a spy, being caught within the enemy's lines without his uniform. Harry sends a letter to his mother telling her of the facts, and she makes an impassioned plea to General Porter, the Southern soldier, for the life of her son, but to no avail. Harry is shot, and a pathetic and dramatic scene takes place as the mother fondles the lifeless body of her boy and calls for vengeance upon the heads of those responsible for his death. A month later General Porter lays plans to crush the North, and sends his son Bob to General Lee with plans of the Union fortifications. Bob has a narrow escape from capture, and in his flight comes upon the home of Mrs. Barnes. With her heart heavy with grief over the death of her son, her sympathy goes out to this hunted youth, and she hides him in the room formerly occupied by Harry. Bob has thrown his coat down, and the letter to Lee drops out. Mrs. Barnes reads it, and in a flash she plans a terrible revenge on General Porter. While Bob is sleeping in thorough exhaustion after his nights of peril, she hides his clothing and substitutes the uniform of her son, and when the Union soldiers come hunting for Bob she helps in his capture and accuses him of being a spy, turning over to the Union officer the letter to Lee and telling him that Bob came there posing as a Northern officer. Bob is arrested and held for trial as a spy. The failure of Bob to deliver the letter leads to a terrific battle, in which the Confederates are driven back. Mrs. Barns, in calm contemplation of her work, realizes what an injustice she has done, and filled with remorse has terrible visions which nearly drive her mad. She finally resolves to appeal to Lincoln, and hurries to him. Her plea is overruled by the cabinet, but when Mrs. Barnes lays Lincoln's old I.O.U. in his hand and demands payment of his obligation, he is persuaded to sign the pardon which is rushed by fleet messengers to save the life of the Southern boy.